A search of the prior art located the following United States Patents which are believed to be representative of the present state of the prior art: U.S. Pat. No. 3,991,932, issued Nov. 16, 1976, U.S. Pat. No. 4,091,985, issued May 30, 1978, U.S. Pat. No. 4,313,555, issued Feb. 2, 1982, U.S. Pat. No. 5,121,878, issued Jun. 16, 1992, U.S. Pat. No. 4,339,041, issued Jul. 13, 1982, U.S. Pat. No. 4,216,897, issued Aug. 12, 1980, U.S. Pat. No. 3,608,811, issued Sep. 28, 1971, U.S. Pat. No. 3,556,384, issued Jan. 19, 1971, U.S. Pat. No. 3,908,889, issued Sep. 30, 1975, and U.S. Pat. No. 3,918,630, issued Nov. 11, 1975.
With reference to the above-identified prior art, it can be seen that it is well known to form trays, covers and the like from unitary blanks of paperboard material. The devices, after assembly, are often held together by corner lock arrangements of various types. Considerable manual or machine manipulation of the blank, in particular at the corners thereof, is often required to assemble the tray or the like. Also, some prior art constructions are characterized by a relatively unstable or unreliable corner construction which can result in failure of the assembled receptacle.